The present invention relates to a method and apparatus for applying stripes to a moving web. More specifically, the present invention relates to a method and apparatus for registering and applying stripes to individual banknotes of banknote sheets.
To deter counterfeiting, credit cards, smart cards, passports, banknotes and other valuable paper documents typically incorporate a variety of security features. One known type of security feature is in the form of a thin film structure comprising a foil substrate and a multi-layer interference coating carried by the substrate. The multi-layer interference coating produces an inherent color shift with a change in viewing angle. This type of security feature has been used on Canadian banknotes. It is of course desired to apply these security features to banknotes quickly, easily and in a cost effective manner without disrupting the banknote printing process.
It is therefore an object of the present invention to provide a novel method and apparatus for applying a stripe disposed on a carrier onto a moving web.
According to one aspect of the present invention there is provided an apparatus for applying a stripe disposed on a carrier onto a moving web comprising:
a drive to advance said carrier from an unwind reel to a take-up reel;
a nip intermediate said unwind reel and said take-up reel through which said carrier and said web pass to apply said stripe to said web; and
a modulator acting on said carrier to modulate the speed of said carrier passing through said nip so that the speed of said carrier passing through said nip coincides generally with the speed of the web passing through said nip without changing the speed at which said carrier is advanced by said drive.
In a preferred embodiment, the web is discontinuous defining successive sheets and wherein the carrier is in the form of a ribbon. The modulator modulates the speed of the ribbon so that it is generally stationary at the nip when gaps between successive sheets occur at the nip. In one form, the modulator includes a reciprocating or oscillating shuttle carrying a roller set adjacent each end thereof and a stationary roller set associated with and in line with each roller set carried by the shuttle. The ribbon is alternately wound around the rollers of one roller set on the shuttle and the rollers of the associated stationary roller set prior to passing through the nip and is alternately wound around the rollers of the other roller set on the shuttle and the rollers of the associated stationary roller set after passing through the nip. In one embodiment, the shuttle includes a cam follower extending therefrom which travels along a track in a rotating cam to cause the shuttle to reciprocate as the cam follower travels along the track. The profile of the track is selected so that the shuttle travels at a generally constant speed in both directions. Alternatively, a motorized stepper or servo drive programmed to follow the cam profile can be used to move the shuttle.
Preferably, the apparatus further includes a ribbon synchronization adjustment unit to shift the ribbon relative to the nip when the ribbon is generally stationary so that when the ribbon is advanced through the nip, the stripe registers with the sheet passing through the nip. In a preferred embodiment, the unit includes a ribbon synchronization adjustment mechanism comprising a frame member carrying rollers at opposed ends thereof. One of the rollers contacts the ribbon before the nip and one of the rollers contacts the ribbon after the nip. A drive moves the frame member laterally in response to a controller. The controller communicates with a first sensor detecting the position of the stripe on the ribbon and a second sensor detecting the position of the sheet relative to the nip and determines whether the ribbon needs to be shifted to register the stripe with the sheet.
According to another aspect of the present invention there is provided an apparatus for applying discrete stripes to individual documents on sheets during a document production process, each of said sheets including a plurality of rows of documents, said stripes being carried by ribbons each of which is associated with a respective row of documents, said apparatus comprising:
a drive to advance said ribbons from unwind reels to take-up reels;
a nip intermediate said unwind reels and said take-up reels through which said ribbons and successive sheets pass to apply said stripes to said documents; and
a ribbon speed modulator acting on said ribbons to modulate the speed of said ribbons passing through said nip so that the speed of said ribbons passing through said nip coincides generally with the speed of the sheets passing through said nip without changing the speed at which said ribbons are advanced by said drive.
According to still yet another aspect of the present invention there is provided in a document production process where stripes disposed on a carrier are applied onto a moving web as the carrier and the web pass through a nip, the carrier being advanced by a generally constant speed drive and the web undergoing changes in speed relative to the nip, the improvement comprising:
a modulator acting on said carrier to modulate the speed of said carrier passing through said nip so that the speed of said carrier passing through said nip coincides generally with the speed of the web passing through said nip without changing the speed at which said carrier is advanced by said drive.
In still yet another aspect of the present invention there is provided a method of applying a stripe disposed on a carrier onto a moving web comprising the steps:
advancing said carrier via a drive through a nip through which said web passes to apply said stripe to said web; and
modulating the speed of said carrier passing through said nip so that the speed of said carrier passing through said nip coincides generally with the speed of the web passing through said nip without changing the speed at which said carrier is advanced by said drive.
The present invention provides advantages in that the ribbon is stopped relative to the nip during a gap between successive sheets passing through the nip to avoid stripe wastage. This is achieved without disrupting the drive advancing the ribbon.